Native tree species differed in their effects on above- and belowground carbon stocks and fluxes in these 16-yr-old experimental plantations at La Selva Biological Station, Costa Rica. Results were explained primarily by differences in growth rates, C allocation, turnover rates, and tissue chemistry. In this experiment established in an abandoned pasture, all five tree species had attained biomass amounts similar to that of nearby mature forest, whereas the abandoned pasture control remained in arrested succession. Carbon sequestration averaged 5.2 Mg∙ha-1∙yr-1 across species, close to the annual per capita fossil-fuel use in the United States of 5.3 Mg C.